Re: opening and reading a character from a file with emu8086 assembler

spamtrap@xxxxxxxxxx schrieb: 
Hi! I am new to assembly. I am currrently writing a program that opens
a file, reads on character at a time and print each character on the
screen. It prints the '$' character in a seemingly infinite loop. Here
is my code:
org 100h            ;.com memory layout


You need a data-segment.

maybe:
mov ax, cs
mov ds, ax

For the beginning you need more stuff like:

Ralf Browns IRQ-List(RBIL)
http://www.pobox.com/~ralf
http://www.pobox.com/~ralf/files.html
ftp://ftp.cs.cmu.edu/afs/cs.cmu.edu/user/ralf/pub/

RBIL->Inter61b.zip->Interrup.f
INT 21 - DOS 2+ - "OPEN" - OPEN EXISTING FILE
	AH = 3Dh
	AL = access and sharing modes (see #01402)
	DS:DX -> ASCIZ filename

mov dx, offset file ;address of file to dx
mov al,0            ;openfile (read-only)
mov ah,3dh
int 21h             ;call the interupt
jc  terminate       ;if error occurs, terminate program
mov bx,ax           ;put handler to file in bx

mov cx,1            ;read one character at a time
print:


mov dx, OFFSET buffer

INT 21 - DOS 2+ - "READ" - READ FROM FILE OR DEVICE
	AH = 3Fh
	BX = file handle
	CX = number of bytes to read
	DS:DX -> buffer for data

mov ah,3fh          ;read from the opened file (its handler in bx)
int 21h
jc  terminate       ;end program if end of file is reached


mov ax,dx           ;char is in dl, send to ax for printing (char is in
al)


No, the byte is stored at ds:buffer.

mov dl, buffer

mov ah,0eh          ;print character
int 10h
jmp print           ;repeat if not end of file

terminate:
ret

file db "c:\input.txt",0

handle dw ? 
    ^
You dont acess this location.

buffer DB ?
;-------------------

Dirk

.

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